VPA is a type of medication normally used to treat seizures and other nervous system problems. It has been found that VPA works against HIV by releasing the virus from resting CD4 cells, allowing other anti-HIV medications to attack it. The purpose of this study is to assess the efficacy of VPA when used in HIV infected participants using highly active antiretroviral therapy (HAART). The expected duration of participation for individually enrolled participants will depend on which study group the participant is placed in but may range from approximately 24 to 144 weeks.